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Old 09-10-2003, 02:55 AM   #61
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Quote:
Originally posted by x_man
Basically the rear tyres will get progressive smaller than the front because of the shift of weight of the car to the back when running in the forward motion and during accelerations.

Even if the front and rear rollout ratio is equal, you will still get this wear because of the shift in weight.
Yes, your explanation sound plausible. Weight biasness has got a lot to do with the rear tires wearing faster. It does not help much that the rear tires need to keep the rear traction of the car especially in the corners and high speed sweepers...

Anyway Master X, I think StepPins wanted to know if he started with the ideal front and rear tire diameters, will get get a better wear profile on the front and rear... Or in order words will the shift in the weight bias be more ideal... I think he wants to achieve an equal wear front and rear tires without creating any front overdrive at the end of a long race. I may be wrong.
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Old 09-10-2003, 03:31 AM   #62
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Quote:
Originally posted by InitialD
Yes, your explanation sound plausible. Weight biasness has got a lot to do with the rear tires wearing faster. It does not help much that the rear tires need to keep the rear traction of the car especially in the corners and high speed sweepers...

Anyway Master X, I think StepPins wanted to know if he started with the ideal front and rear tire diameters, will get get a better wear profile on the front and rear... Or in order words will the shift in the weight bias be more ideal... I think he wants to achieve an equal wear front and rear tires without creating any front overdrive at the end of a long race. I may be wrong.
Will be quite difficult for him to do that if not impossible!! Unless the weight bias when the car is running is equal in the front and rear. Or he can use a softer front but that would gives a lot of steering and the car may be quite twitchy to control.

Basically the area of contact of our 4wd touring car to the ground is concentrated at the rear tyres hence they tends to wear off faster the front. Unless he uses a harder rear compound which gives the same effect as i mentioned above.
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Old 09-10-2003, 04:02 AM   #63
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Quote:
Originally posted by x_man
Basically the rear tyres will get progressive smaller than the front because of the shift of weight of the car to the back when running in the forward motion and during accelerations.

Even if the front and rear rollout ratio is equal, you will still get this wear because of the shift in weight.
Basically the rears wear more because are a different foam compound with different cell construction to have better grip. With the same shore rating, rears wear more than fronts.

In fact, Italian foam builders (GRP, Enneti and some non italian like Yokomo) use what they call 'Japanese foam' for the fronts and 'European Foam' for the rears. True a set of fronts and one of rears and see the difference, Rears have a much smaller cell construction.

Other manufacturers (Zac, Speedmind and Take Off - AFAIK) use multiring and/or Japanese foam for the rears too giving a complete different feeling, be warned about this if you switch to multiring rears you need to go one hardness down aas a ballpark (From 40 to 37, 43 to 40 and so on). Many people don't realize this and got scated doing a quick change of tyres for testing 'something different'.
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Old 09-10-2003, 04:37 AM   #64
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Quote:
Originally posted by Corse-R
Other manufacturers (Zac, Speedmind and Take Off - AFAIK) use multiring and/or Japanese foam for the rears too giving a complete different feeling, be warned about this if you switch to multiring rears you need to go one hardness down aas a ballpark (From 40 to 37, 43 to 40 and so on). Many people don't realize this and got scated doing a quick change of tyres for testing 'something different'.
Correct me if I'm wrong but I thought multiring type tires consist of different compounds on one rim? Usually harder compound on the outside of the tire to prevent the tire walls from chunking. Is this correct?

I think most tires sold are multiring type if I'm not mistaken.
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Old 09-10-2003, 04:46 AM   #65
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Quote:
Originally posted by InitialD
Correct me if I'm wrong but I thought multiring type tires consist of different compounds on one rim? Usually harder compound on the outside of the tire to prevent the tire walls from chunking. Is this correct?

I think most tires sold are multiring type if I'm not mistaken.
Probably true, but all the multiring tyres I've used were of the same shore hardness all the width of the tyre, main difference vs. to a 'uni-ring' tyre was the relative hardness due to the additional glue to join all the donuts (more side stiffness).

Have seen some tyres with different compounds (MicroSystems have some part no with split compounds) on the inner/outer side (like plaids or orange/blue compounds). But are very scarce to see and delicate of using just by the difference of hardness.
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Old 09-10-2003, 06:07 AM   #66
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Quote:
Originally posted by InitialD
Correct me if I'm wrong but I thought multiring type tires consist of different compounds on one rim? Usually harder compound on the outside of the tire to prevent the tire walls from chunking. Is this correct?

I think most tires sold are multiring type if I'm not mistaken.
We use Active tyres - Japanese rubber front and rear.
Their "normal" tyres have two rings, always placed evenly tyre to tyre but the multi-ring tyres are made up of about five rings - all the same shore.
Our experience is much like Corse-R's. Going from 37's to 37 Multi's is a handy method of going about a half step harder, probably due to the gluing of the extra rings. The multi's are supposed to be more stable, but haven't really noticed it since you can't really compare properly.

We usually take an angle cut of about 80 from the rim to help prevent chunking. It seems to me that chunking mostly happens from insufficient camber, excessive droop and of course lateral traversal of inhospitable terrain.
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Old 09-10-2003, 07:18 AM   #67
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Quote:
Originally posted by Taylor-Racing
We usually take an angle cut of about 80 from the rim to help prevent chunking. It seems to me that chunking mostly happens from insufficient camber, excessive droop and of course lateral traversal of inhospitable terrain.
Many times I saw that people insist on keeping the shoulders of their freshly cut tyres square and very sharp (is the best way to rip and chunk a tyre, no matter the diameter).

I make the shoulders rounded and don't have any problems with tyre chunking, people argue that making round the shoulders you lose 1 or 2mm width on the thread, but prefeer to lose it and have a slight better cornering because they 'hook' a little less, but rotate much better. Will try to find a photo of how I cut mine tyres.
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Old 09-10-2003, 07:35 AM   #68
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Quote:
Originally posted by Corse-R
but prefeer to lose it and have a slight better cornering because they 'hook' a little less, but rotate much better. Will try to find a photo of how I cut mine tyres.
yeah you will find that if you don't round the outside corner of the tire and the inside a little also that you will get a "on/off" feeling steering response. the steering will not be as smooth and progressive if you leave the edge square and yep it will chunk easier.

also by rounding it the weight shifting from left/right is smoother. imagine a 1;1 car with the sidwalls of the tire being right angled and hard. it wouldn't steer very nicely would it! you are actually getting more grip becouse the tire can have a larger contact patch when it is leaning on the outside shoulder of the tire, due to the rounded edge.
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Old 09-10-2003, 08:27 AM   #69
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Agreed - we round the shoulders off as well - quite a lot really.
I don't think we lose anything by doing so.

I also find that tyres go "off" quite quickly. There is a marked difference in grip between fresh new tyres and older ones. This means it's difficult to collect tyres of a specific diameter for an important competition. Currently it's winter here and all our (harder) summer tyres are safely stored in Pringles tubes.
Yes, I ate the Pringles, first.
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Old 09-10-2003, 03:33 PM   #70
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I didn't want to do this StepPins (because I'm a sneaky thief ), but here goes. I found my car to handle best with the rollcenter as it is right now, with tires around 61-58mm in height. This worked ridiculously well, or so I thought (still do infact, so it should be, "I think" ). Probably a little different for your car though. By thetime it got down to 57 and 56mm, it got a little bit more skatey.

Jeez, can't give away all my trade secrets... wait, I think that was my last one... shoot, I'm an idiot .
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Old 09-11-2003, 02:18 AM   #71
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As far as multiring foam tires (rears), I did experience a different "feeling" of the car. I usually use GRP/Power Tyres, 40 shore front and rear. I tried using the same shore, but in a different brand -- ZAC projects multiringed rears and regular fronts. I felt as if I had more steering, but most of it was comming from the rear. What you guys had stated about multiring tires makes alot of sense
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Old 09-11-2003, 05:05 AM   #72
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Default The trick

Hey drfritz, tats a very interesting trick ! but i have a question, hence tat 1/8 tire are bigger diameter than 1/10... May i know how do u mount on to smaller rim and using wat to glue on ??



Quote:
Originally posted by drfritz

If you are running on a race program that has 1/8 running with you at the same location, ask the 1/8 racers to give you there worn out tires, 90% of the time they will say no problem sence they are to small for there cars and after all there just going to toss them. sock them in acetone over night, pull the rubber of the rims, sock the rubber in HOT water to get the acetone out of the rubber, if you do not do these it will make the rubber harder,then rinse in cold wate and let dry, you are ready to mount them on some rims, you did save your worn out 1/10 foams did you not? do the same, soke them in the acetone to remove the old rubber I can get away with only having to buy on set to every 4 I make and that has saved me over five hunders dollars this year alone....
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Old 09-14-2003, 03:28 AM   #73
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Arrow Shore ratings

I know that foam tire shore ratings tell how soft the foam compound is. What I'm curious about is are those shores related to track temps also? -- i.e., rubber tire ratings.
And how are foams properly chosen? I know if it works, go for it and keep using them. But coning can come into affect and may suede the user to try either lower or higher shore ratings.
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Old 09-14-2003, 03:43 AM   #74
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Default Re: Shore ratings

Quote:
Originally posted by StepPins
I know that foam tire shore ratings tell how soft the foam compound is. What I'm curious about is are those shores related to track temps also? -- i.e., rubber tire ratings.
And how are foams properly chosen? I know if it works, go for it and keep using them. But coning can come into affect and may suede the user to try either lower or higher shore ratings.
Shore is a hardness rating - no relationship to temp's.
Tyre choice is something you'll get the hang of - to start out, just ask someone at the track. It's quite possible to find yourself on a soft tyre which makes the car too difficult to drive - a harder tyre, while having less grip, may actually be faster. You might also find that a softer tyre is good in the morning and a harder one is needed as the traction improves during the day.
Coning is really a set-up issue - adjust camber so they wear flat.
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Old 09-16-2003, 01:26 AM   #75
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Default Re: Shore ratings

Quote:
Originally posted by StepPins
...And how are foams properly chosen?

Lap times ... sorry but true. The right choice shouldn't have a ton of girp, but allow the car to float around a turn, while keeping a tight and consistent line throughout the corner. Some people just go too soft and achieve a similar result *cough* Taka *cough* . Generally, too soft will feel too tight... not want to do much but have tons of traction.
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